Although the hypothesis that the proliferation of the committed granulocyte-macrophage stem cell is regulated by two possible mechanisms: a positive feedback involving CSF on the one hand and a negative feedback involving PGE on the other hand has stimulated considerable interest in the role of prostaglandins (PGs) in hemopoiesis, there is very limited information on the capacity of these cells to make the variety of prostaglandins that are known to exist. It's our objective therefore: (i) To determine the capacities of: (a) chloroma cells (a malignant proliferacting cell line in continous culture); (b) freshly isolated cells from subcutaneous tumors excised from rats previusly injected with chloroma cells; and (c) the turpentine-induced hyperplastic bone marrow cells (a non-malignant proliferating cells) to transform arachidonic acid into PGE2, PGD2 and PGF2 Alpha Further studies are planned to determine whether thromboxane A2, prostacyclin (PGI2) and the non-cyclic hydroxy fatty acids are also synthesized; (ii) To test the effects of two purified CSF materials (from pancreatic carcinoma cells and human lung) on the hydrolysis and release of arachindonic acid from prelabeled cells in culture; (iii) to determine the capacity of the cells to transform PGE2 into PGF2 Alpha (a proliferating molecule; (iv) To determine whether or not recepotrs for PGE2 PGD2 and PGF2 Alpha are present on the cell membranes; to study their properties and to determine whether or not they are altered during the hyperproliferative process; (v) To evaluate the above biochemical parameters in Friend's virus-induced erythroleukemic cells and other tumor cells in order to determine whether or not a common pattern of alteration does occur in malignant cells. Methods involve the use of 14C-arachidonic acid which will be incubated with cell suspensions to determine its transformation by cells into the variety of PGs and other non-cyclic hydroxy acids. Identification will be by separation on various TLC systems and dilution with authentic standards. Receptor studies will involve binding reactions of isolated cell membranes and tritiated PGE2, PGD2 or PGF2 Alpha. Bound and unbound ligands will be separated by Sephadex chromatography and Scatchard plot made from the equilibrium data.